UV light source

ABSTRACT

There is described an ultraviolet light source comprising an ultraviolet lamp, a microwave energy source for exciting said ultraviolet lamp and an enclosure for enclosing the ultraviolet lamp, the enclosure comprising an optically transparent waveguide. The ultraviolet light source is particularly suitable for use in the promotion of photochemical reactions and of molecular dissociation in liquids.

This application is the national phase under 35 U.S.C. §371 of PCTInternational Application No. PCT/EP00/07288 which has an Internationalfiling date of Jul. 26, 2000, which designated the United States ofAmerica and was published in English.

TECHNICAL FIELD

The present invention is in the field of ultraviolet (UV) light sources.

BACKGROUND OF THE INVENTION

It is known to use ultraviolet (UV) radiation for a variety of usesincluding those involving the promotion of photochemical reactions andof molecular dissociation.

One problem with known systems is that it is difficult to safely providesufficient excitation energy to the UV source and difficult toeffectively transfer that energy to the substance or entity to betreated. It is therefore difficult to arrange systems for high energy,high throughput industrial purposes.

There is now described an ultraviolet light source which enablesefficient, high throughput UV treatment to be conducted. The ultravioletlight source comprises an UV lamp which is excited by a microwave energysource. The lamp is enclosed by a waveguide comprising UV transparentmaterial. The ultraviolet light source is particularly suitable for thetreatment of liquids which are flowed past the ultraviolet light source.

SUMMARY OF THE INVENTION

According to one aspect of the present invention there is provided anultraviolet light source comprising an ultraviolet bulb; a microwaveenergy source for exciting said ultraviolet bulb; and an enclosure forenclosing the ultraviolet bulb, the enclosure comprising an opticallytransparent waveguide.

The dominant wavelength of the ultraviolet light source is either

(a) from 140 to 240 nm, preferably from 150 to 220 nm, most preferablyfrom 160 to 200 nm, particularly 182 nm or 185 nm and the ultravioletlight source is suitable for use in promoting molecular dissociationreactions; or

(b) from 300 to 400 nm, preferably from 320 to 380 nm, most preferablyfrom 330 to 370 nm, particularly 346 nm and the ultraviolet light sourceis suitable for use in promoting photochemical reactions.

By optically transparent waveguide it is meant a waveguide that issubstantially transparent to the ultraviolet radiation employed herein,typically having a transparency of greater than 50%, preferably greaterthan 90% to UV radiation.

The waveguide controls the flow of ultraviolet radiation from theenclosure. The control function typically includes the prevention of therelease of harmful or unnecessary ultraviolet radiation frequencies. Theexact nature of the waveguide and its control function can be tailoredto fit the purpose of use.

Suitably, the ultraviolet bulb has no electrode. That is to say it is anelectrode-less bulb such as one comprising a partially evacuated tubecomprising an element or mixtures of elements in vapour form. Mercury isa preferred element for this purpose, but alternatives include mixturesof inert gases with mercury compounds, sodium and sulphur. Halides, suchas mercury halide are also suitable herein. Amalgams are also suitableherein including indium/mercury amalgam.

In one aspect, the waveguide controls the flow of microwave energy fromthe enclosure. Control of the microwave energy which passes through thewaveguide is useful in embodiments of the invention which make use ofboth UV and microwave radiation.

In another aspect, the waveguide blocks at least the majority of theflow of microwave energy from the enclosure.

Suitably, the enclosure comprises quartz or a UV-transparent plasticmaterial.

Suitably, the enclosure is coated with a coating which assists incontrolling the flow of ultraviolet and/or microwave energy therefrom.The coating may be applied to either or both of the inner or outersurfaces of the enclosure. Partial coatings are also envisaged.

Suitably, a system for cleaning the enclosure (e.g. the quartz tube) isincorporated herein. Suitable cleaning systems include those based uponfluid flow, such as flow of water, air or gas. Cleaning agents such asdetergents may be employed as necessary.

Suitably, the waveguide comprises a conducting material. The conductingmaterial may be integral, or applied as an internal or external coatingor liner. The liner may directly contact the inner surface of theenclosure or be spaced therefrom.

Suitably, the waveguide comprises a conducting mesh. Preferably, theconducting mesh comprises a high frequency conducting material selectedfrom the group consisting of copper, aluminium and stainless steel.

The ultraviolet bulb has any suitable shape and size, including elongateforms such as a cigar-shape. The bulb size can be tailored. Typical bulbdiameters are from 5 to 200 mm, for example 38 mm.

Embodiments are envisaged in which plural bulbs are employed. The bulbmay be similar in type e.g. of similar size and operating temperature orcombinations of different bulb types may be employed. The number ofbulbs employed is tailored to the purpose of use. Typically from 2 to 25bulbs are employed, such as from 3 to 18 bulbs. Various forms ofarrangement of the plural bulbs are envisaged including random orinformal arrangements, side-by-side arrangements, sequentialarrangements, array arrangements and clusters. The bulbs may be arrangedin serial, parallel or mixed serial and parallel electrical circuitarrangements.

The optically transparent waveguide has any suitable shape, such ascylindrical or rectangular forms. The length and size of the waveguideis tailored to fit the particular purpose of use and to accommodate thenecessary bulb(s).

Suitably, the ultraviolet bulb has an operating temperature whichmaximises the chosen bulb characteristics. Typical operatingtemperatures are from 10° C. to 900° C., and the operating temperaturewill be selected and optimised according to the purpose of use.

Suitably, the microwave energy source comprises a magnetron. Alternativesources are envisaged such as solid state devices.

Suitably, the ultraviolet light source additionally comprises a systemfor cleaning the enclosure.

Suitably, the ultraviolet light source additionally comprises apathguide to guide the microwave energy from the microwave energy sourceto the ultraviolet bulb.

In one aspect the pathguide defines an essentially linear path for themicrowave energy.

In another aspect, the pathguide defines a non-linear path such as apath defining an angle, such as a right angle.

Suitably, the pathguide comprises a coaxial cable.

Suitably, the ultraviolet light source additionally comprises a housingfor said enclosure. Preferably, the housing has an inlet and an outletand the housing is shaped to guide fluid flow from the inlet, past theenclosure to the outlet. Preferably, the fluid comprises air or a liquidsuch as water. Suitably, the ultraviolet light source additionallycomprises a pump for pumping fluid from the inlet, past the enclosure tothe outlet. Alternatively, gravity may be utilised to encourage fluidflow.

The choice of materials for use in the housing and any fluid flow pipingarrangements can be important. Typically, the materials will be selectedwhich are resistant to corrosion and which do not leach contaminants tothe system.

Seal materials are also carefully selected with typical seal materialsincluding Chemraz (trade name), Teflon (trade name), encapsulated Viton(trade name) and GORE-TEX (trade name).

According to another aspect of the present invention there is provided alamp comprising an ultraviolet bulb, said bulb being excitable bymicrowave energy; and an enclosure for enclosing the ultraviolet bulb,the enclosure comprising an optically transparent waveguide.

The dominant wavelength of the lamp is either

(a) from 140 to 240 nm, preferably from 150 to 220 nm, most preferablyfrom 160 to 200 nm, particularly 182 nm or 185 nm and the lamp issuitable for use in promoting molecular dissociation reactions; or

(b) from 300 to 400 nm, preferably from 320 to 380 nm, most preferablyfrom 330 to 370 nm, particularly 346 nm and the lamp is suitable for usein promoting photochemical reactions.

Preferably, the ultraviolet bulb has no electrode.

According to a further aspect of the present invention there is provideda method of promoting the dissociation of a molecular entity comprising

applying microwave energy to an ultraviolet lamp to produce ultravioletradiation of dominant wavelength of from 140 to 240 nm; and

exposing the molecular entity to said ultraviolet radiation, wherein

an enclosure encloses the ultraviolet lamp, the enclosure comprising anUV transparent waveguide.

In one aspect, the molecular entity is borne in a fluid such as air or aliquid and the fluid flows past the enclosure. A specific example ofthis is in the clean up of ballast seawater from the holds of shipswherein contaminants in the ballast water are dissociated by applicationof ultraviolet radiation.

A further specific example of molecular dissociation applications basedon fluid flow is in the dissociation of organic material, such as TotalOxidisable Carbon (TOC) in rinse water for use in the electronics,semiconductors pharmaceuticals, beverage, cosmetics and powerindustries. The process involves the production of OH.radicals whichoxidise any hydrocarbon molecules in the rinse water. Optionally, otheroxidants may be employed such as ozone and hydrogen peroxide. Typically,polishing deionisation beds, featuring nuclear-grade resin materials areplaced downstream of the TOC reduction units to remove any ionisedspecies and restore the resitivity of the water.

In another aspect, the molecular entity is borne on a surface and theultraviolet radiation is applied to the surface. The molecular entitymay, for example be a contaminant on the surface which is renderedharmless by its molecular dissociation.

In one example, the surface is of a food product such as a meat, dairy,fish, fruit or vegetable product and the ultraviolet radiation isapplied to the surface to dissociate any contaminants such as chemicalresidues including pesticides.

In another example, the surface is an industrially-produced product suchas a packaging product for example, a medical packaging product, a foilbag, cup or lid, or a glass or plastic bottle, and the ultravioletradiation is applied to the surface to dissociate any contaminantsarising from the industrial process.

In a further example, the surface is the surface of any equipment usedin the manufacture of food products or industrially produced productssuch as the surface of any reactors or conveyors.

According to a still further aspect of the present invention there isprovided a method of promoting a photochemical reaction in a substancecomprising

applying microwave energy to an ultraviolet lamp to produce ultravioletradiation of dominant wavelength of from 300 to 400 nm; and

exposing the entity to said ultraviolet radiation, wherein

an enclosure encloses the ultraviolet lamp, the enclosure comprising anUV transparent waveguide.

In one aspect, the substance is borne in a fluid such as air or a liquidand the substance-bearing fluid flows past the enclosure.

In another aspect, the substance is borne on a surface and theultraviolet radiation is applied to the surface.

Preferably, the substance is selected from the group consisting ofsurface treatment materials including paints, toners, varnishes (e.g.polyurethane varnishes), stains and laminating materials.

Laminating is for example, used in the production of various electroniccomponents, data storage devices including compact discs and packagingmaterials including blister packages.

According to a further aspect of the present invention there is providedan ultraviolet light source comprising a plurality of ultraviolet bulbs;a microwave energy source for exciting said plurality of ultravioletbulbs; and an enclosure for enclosing the plurality of ultravioletbulbs, the enclosure comprising an optically transparent waveguide.

According to a further aspect of the present invention there is provideda lamp comprising a plurality of ultraviolet bulbs, said plurality ofbulbs being excitable by microwave energy; and an enclosure forenclosing the plurality of ultraviolet bulbs, the enclosure comprisingan optically transparent waveguide.

BRIEF DESCRIPTION OF THE DRAWINGS

Preferred embodiments of the ultraviolet light source in accord with thepresent invention will now be described with reference to theaccompanying drawings in which:

FIG. 1 is a schematic representation of a first ultraviolet light sourceherein;

FIGS. 2a and 2 b are schematic representations of second and thirdultraviolet light sources herein;

FIGS. 3a and 3 b are schematic representations of fourth and fifthultraviolet light sources herein;

FIG. 4 is a schematic representation of a sixth ultraviolet light sourceherein suitable for use in combined UV and microwave methods;

FIG. 5 is a schematic representation of a seventh ultraviolet lightsource herein;

FIG. 6 is a schematic representation of an eighth ultraviolet lightsource herein;

FIG. 7 is a schematic representation of a ninth ultraviolet light sourceherein; and

FIG. 8 is a schematic representation of a tenth ultraviolet light sourceherein.

FIG. 9 is a cross-sectional view of an ultraviolet lamp herein.

DETAILED DESCRIPTION OF THE INVENTION

The present invention is here described by means of examples, whichconstitute possible embodiments of the invention.

FIG. 1 shows an ultraviolet light source comprising an ultraviolet lamp10 enclosed by cylindrical enclosure 20. The cylindrical walls of theenclosure 20 form a waveguide and are comprised of quartz material whichis transparent to UV radiation. A conducting copper mesh 30 is providedto the inner surface of the waveguide. First end of the cylindricalenclosure has blocking end flange 22 provided thereto. The second end isprovided with coupling flange 24 which couples with right angledpathguide 40 which in turn connects with rectangular pathguide 50.Magnetron 60 acts as a microwave energy source to feed microwaves intothe rectangular waveguide 50, thence into the right angled pathguide 40and finally to the ultraviolet lamp 10 which is excited thereby.

The enclosure 20 is within tubular housing 70. The housing 70 has afluid inlet 72 and a fluid outlet 74 provided thereto. In use, fluidflows from the inlet 72 past the enclosure 20 and towards the outlet 74.As the fluid flows past the enclosure 20 it is irradiated with UVradiation produced by the ultraviolet lamp 10. The radiation itselfpasses through the UV transparent walls of the enclosure 120 a, 120 b tocontact the fluid.

FIGS. 2a and 2 b show related ultraviolet light sources herein. Bothcomprise ultraviolet mercury discharge lamp 110 a, 110 b enclosed bycylindrical enclosure 120 a, 120 b. The cylindrical walls of theenclosure 120 a, 120 b form a waveguide and are comprised of quartzmaterial which is transparent to UV radiation. A conducting copper mesh130 a, 130 b is provided to the inner surface of the waveguide. Theenclosure 120 a, 120 b has air or nitrogen circulating therein. Firstend of the cylindrical enclosure has blocking end flange 122 a, 122 bprovided thereto. The second end is provided with coupling flange 124 a,124 b which couples with water-tight chamber 150 a, 150 b which containsbrass waveguide 140 a, 140 b and magnetron 160 a, 160 b. The magnetron160 a, 160 b acts as a microwave energy source to feed microwaves intothe brass waveguide 140 a, 140 b and thence to the ultraviolet lamp 110a, 110 b which is excited thereby.

The enclosure 120 a, 120 b is within tubular housing 170 a, 170 b. Thehousing 170 a, 170 b has a fluid inlet 172 a, 172 b and a fluid outlet174 a, 174 b provided thereto. In use, fluid flows from the inlet 172 a,172 b past the enclosure 120 a, 120 b and towards the outlet 174 a, 174b. As the fluid flows past the enclosure 120 a, 120 b it is irradiatedwith UV radiation produced by the ultraviolet lamp 110 a, 110 b. Theradiation itself passes through the UV transparent walls of theenclosure 120 a, 120 b to contact the fluid.

FIGS. 3a and 3 b show ultraviolet light sources similar in structure tothe ultraviolet light sources of FIGS. 2a and 2 b but for use intreatment of airborne substances. Both comprise ultraviolet mercurydischarge lamp 210 a, 210 b enclosed by cylindrical enclosure 220 a, 220b. The cylindrical walls of the enclosure 220 a, 220 b form a waveguideand are comprised of quartz material which is transparent to UVradiation. A conducting copper mesh 230 a, 230 b is provided to theinner surface of the waveguide. The enclosure 220 a, 220 b has air ornitrogen circulating therein. First end of the cylindrical enclosure hasblocking end flange 222 a, 222 b provided thereto. The second end isprovided with coupling flange 224 a, 224 b which couples with airtightchamber 250 a, 250 b containing brass waveguide 240 a, 240 b andmagnetron 260 a, 260 b. The magnetron 260 a, 260 b acts as a microwaveenergy source to feed microwaves into brass waveguide 240 a, 240 b andthence to the ultraviolet lamp 210 a, 210 b which is excited thereby.

The enclosure 220 a, 220 b is within tubular housing 270 a, 270 b. Thehousing 270 a, 270 b has an air inlet 272 a, 272 b and an air outlet 274a, 274 b provided thereto. In use, air flows from the inlet 272 a, 272 bpast the enclosure 220 a, 220 b and towards the outlet 274 a, 274 b. Asthe air flows past the enclosure 220 a, 220 b it is irradiated with UVradiation produced by the ultraviolet lamp 210 a, 210 b. The radiationitself passes through the UV transparent walls of the enclosure 220 a,220 b to contact the air, thereby treating the molecular entitiescarried in the air.

FIG. 4 shows a cabinet ultraviolet light source herein suitable for usein treating objects herein. Ultraviolet mercury discharge lamp 310 isenclosed by cylindrical enclosure 320. The cylindrical walls of theenclosure 320 form a waveguide and are comprised of quartz materialwhich is transparent to UV radiation but only partially transparent tomicrowave radiation. A conducting copper mesh 330 is provided to theinner surface of the waveguide. The enclosure 320 optionally has air ornitrogen circulating therein. First end of the cylindrical enclosure hasblocking end flange 322 provided thereto. The second end is providedwith coupling flange 324 which couples with linear pathguide 340 whichin turn connects with magnetron 360. The magnetron 360 acts as amicrowave energy source to feed microwaves into pathguide 340 and thenceto the ultraviolet lamp 310 which is excited thereby.

The enclosure 320 is within housing 370 which has an entry door 380provided thereto. In use, items to be treated are placed in the housing370. The items are irradiated with UV radiation produced by theultraviolet lamp 310 and by microwave radiation deriving from themagnetron 360. The radiation itself passes through the UV transparentand microwave partially transparent walls of the enclosure 320 tocontact the items. Optionally, the housing 370 may be provided with UVtransparent shelves for the items. An inner reflective lining, forexample an aluminium foil lining, may also be provided to the housing370.

FIG. 5 shows an ultraviolet light source comprising an ultraviolet bulb410 enclosed by cylindrical enclosure 420. The cylindrical walls of theenclosure 420 form a waveguide and are comprised of quartz materialwhich is transparent to UV radiation. The quartz tube enclosure 420 isprovided with a cleaning system comprising wiper 480 which is mountedfor movement on track 482. The track 482 is arranged parallel to theenclosure 420 and the movement of the wiper 480 is powered by motor 484.

A conducting copper mesh 430 is provided to the inner surface of thewaveguide. An end of the enclosure 420 couples with coupling flange 424which couples with stainless steel cylindrical pathguide 440 which inturn connects with stainless steel rectangular pathguide 450. Magnetron460 acts as a microwave energy source to feed microwaves into therectangular pathguide 450, thence into the cylindrical pathguide 440 andfinally to the ultraviolet lamp 410 which is excited thereby.

The enclosure 420 is within stainless steel housing 470. The housing 470has a fluid inlet 472 and a fluid outlet 474 provided thereto. In use,fluid flows from the inlet 472 past the enclosure 420 and towards theoutlet 474. As the fluid flows past the enclosure 420 it is irradiatedwith UV radiation produced by the ultraviolet bulb 410. The radiationitself passes through the UV transparent walls of the enclosure 420 tocontact the fluid.

FIG. 6 shows an ultraviolet light source comprising two ultravioletbulbs 510, 511 fixed in a mutually parallel arrangement by lamp supports514, 515. The bulbs 510, 511 are enclosed by cylindrical enclosure 520.An air coolant system is provided to the bulb 510 wherein cooling air isfed into the enclosure 520 through air inlet 526 and circulates past thebulb before exiting at air outlet 528. The cylindrical walls of theenclosure 520 form a waveguide and are comprised of quartz materialwhich is transparent to UV radiation. The quartz tube enclosure 520 isprovided with a cleaning system comprising wiper 580 which is mountedfor movement on track 582. The track 582 is arranged parallel to theenclosure 520 and the movement of the wiper 580 is powered by motor 584.

A conducting copper mesh 530 is provided to the inner surface of thewaveguide. An end of the enclosure 520 couples with coupling flange 524which couples with stainless steel rectangular pathguide 550. Magnetron560 acts as a microwave energy source to feed microwaves into therectangular pathguide 550 and thence to the ultraviolet lamp 510 whichis excited thereby.

The enclosure 520 is within stainless steel housing 570 havingobservation port 571. The housing 570 has a fluid inlet 572 and a fluidoutlet 574 provided thereto. In use, fluid flows from the inlet 572 pastthe enclosure 520 and towards the outlet 574. As the fluid flows pastthe enclosure 520 it is irradiated with UV radiation produced by theultraviolet bulbs 510, 511. The radiation itself passes through the UVtransparent walls of the enclosure 520 to contact the fluid.

FIG. 7 shows an ultraviolet light source comprising two ultravioletbulbs 610, 611 fixed in a mutually parallel arrangement by lamp supports614, 615. The bulbs 610, 611 are enclosed by cylindrical enclosure 620.An air coolant system is provided to the bulbs 610, 611 wherein coolingair is fed into the enclosure 620 through air inlet 626 and flows pastthe bulbs 610, 611 before exiting at air outlets 628, 629. Thecylindrical walls of the enclosure 620 form a waveguide and arecomprised of quartz material which is transparent to UV radiation. Thequartz tube enclosure 620 is provided with a cleaning system comprisingwiper 680 which is mounted for movement on track 682. The track 682 isarranged parallel to the enclosure 620 and the movement of the wiper 680is powered by motor 684.

A conducting copper mesh 630 is provided to the inner surface of thewaveguide. An end of the enclosure 620 couples with coupling flange 624which couples with stainless steel rectangular pathguide 650. Magnetron660 acts as a microwave energy source to feed microwaves into therectangular pathguide 650 and thence to the ultraviolet bulbs 610, 611which are excited thereby.

The enclosure 620 is within stainless steel housing 670 havingobservation port 671. The housing 670 has a fluid inlet 672 and a fluidoutlet 674 provided thereto. In use, fluid flows from the inlet 672 pastthe enclosure 620 and towards the outlet 674. As the fluid flows pastthe enclosure 620 it is irradiated with UV radiation produced by theultraviolet bulbs 610, 611. The radiation itself passes through the UVtransparent walls of the enclosure 620 to contact the fluid.

FIG. 8 shows an ultraviolet light source based on a series arrangementof a pair of ultraviolet light sources of the type illustrated in FIG.7. The ultraviolet source comprises two pairs of ultraviolet bulbs 710a, 711 a and 710 b, 711 b fixed in a mutually parallel arrangement bylamp supports 714 a, 715 a and 714 b, 715 b. The bulbs 710 a, 711 a and710 b, 710 b are each enclosed by cylindrical enclosures 720 a, 720 b.An air coolant system is provided each pair of bulbs 710 a, 711 a and710 b, 711 b wherein cooling air is fed into the enclosures 720 a, 720 bthrough air inlets 726 a, 726 b and flows past the bulbs 710 a, 711 aand 710 b, 711 b before exiting at air outlets 728 a, 729 a and 728 b,729 b. The cylindrical walls of the enclosures 720 a, 720 b form awaveguide and are comprised of quartz material which is transparent toUV radiation. The quartz tube enclosures 720 a, 720 b are each providedwith a cleaning system comprising wiper 780 a, 780 b which is mountedfor movement on respective track 782 a, 782 b. The tracks 782 a, 782 bare arranged parallel to the enclosures 720 a, 720 b and the movement ofthe wipers 780 a, 780 b is powered by motors 784 a, 784 b.

A conducting copper mesh 730 a, 730 b is provided to the inner surfaceof the waveguide. An end of each enclosure 720 a, 720 b couples withcoupling flange 724 a, 724 b which couples with stainless steelrectangular pathguide 750 a, 750 b. Magnetrons 760 a, 760 b act asmicrowave energy sources to feed microwaves into the respectiverectangular pathguides 750 a, 750 b and thence to the ultraviolet bulbs710 a, 711 a and 710 b, 711 b which are excited thereby.

The enclosures 720 a, 720 b are within a stainless steel housingcomprising two interconnected arms 770 a, 770 b each having anobservation port 771 a, 771 b. The first arm of the housing 770 a has afluid inlet 772 and the second arm of the housing 770 b has a fluidoutlet 774 provided thereto. In use, fluid flows from the inlet 772 pastthe first enclosure 720 a, through passages 773 a, 773 b, then past thesecond enclosure 720 b and finally towards the outlet 774. As the fluidflows past the enclosures 720 a, 720 b it is irradiated with UVradiation produced by the ultraviolet bulbs 710 a, 711 a and 710 b, 711b. The radiation itself passes through the UV transparent walls of theenclosures 720 a, 720 b to contact the fluid.

Whilst in each of FIGS. 1 to 8 the magnetron is arranged locally to thelamp it may be appreciated that in other embodiments the magnetron isdistally located and communicates with the lamp via a coaxial cable feedarrangement. Such coaxial cable feed arrangements are known in the artfor example, described in Japanese Patent Publication No. 61046290.

FIG. 9 shows in cross-sectional view an ultraviolet lamp herein. Thelamp comprises two rows 810 a, 810 b of six bulbs forming a six by twolamp array arrangement. The array of bulbs 810 a, 810 b is surrounded bya copper mesh 830 having a rectangular cross-section. Both the array ofbulbs 810 a, 810 b and the copper mesh 830 are enclosed by a quartz tube820 having a circular cross-section.

It may be appreciated that lamps comprising plural bulbs in any suitablearrangement may be employed in variations of the ultraviolet lightsources shown in FIGS. 1 to 8.

What is claimed is:
 1. An ultraviolet light source comprising anultraviolet bulb; a microwave energy source for exciting saidultraviolet bulb; and an optically transparent waveguide for guidingmicrowave energy originating from said microwave energy source to theultraviolet bulb, wherein said waveguide wholly surrounds theultraviolet bulb, and wherein the dominant wavelength of the ultravioletlight source is either (a) from 140 to 240 nm and the ultraviolet lightsource is suitable for use in promoting molecular dissociationreactions; or (b) from 300 to 400 nm and the ultraviolet light source issuitable for use in promoting photochemical reactions.
 2. An ultravioletlight source according to claim 1, wherein the dominant wavelength ofthe ultraviolet light source is from 160 to 200 nm.
 3. An ultravioletlight source according to claim 1, wherein the dominant wavelength ofthe ultraviolet light source is from 330 to 370 nm.
 4. An ultravioletlight source according to claim 1, wherein the ultraviolet bulb has noelectrode.
 5. An ultraviolet light source according to claim 1, whereinthe waveguide controls the flow of microwave energy therefrom.
 6. Anultraviolet light source according to claim 5, wherein the waveguideblocks a majority of the flow of microwave energy therefrom.
 7. Anultraviolet light source according to claim 1, wherein the waveguidecomprises quartz or a UV-transparent plastic material.
 8. An ultravioletlight source according to claim 1, wherein the waveguide comprises aconducting material.
 9. An ultraviolet light source according to claim8, wherein the conducting material is a coating or liner to thewaveguide.
 10. An ultraviolet light source according to claim 8, whereinthe waveguide comprises a conducting mesh.
 11. An ultraviolet lightsource according to claim 10, wherein the conducting mesh comprises amaterial selected from the group consisting of copper, aluminium andstainless steel.
 12. An ultraviolet light source according to claim 1,wherein the ultraviolet bulb has an elongate form.
 13. An ultravioletlight source according to claim 1, comprising plural ultraviolet bulbs.14. An ultraviolet light source according to claim 13, comprising from 2to 25, preferably from 3 to 18 bulbs.
 15. An ultraviolet light source toclaim 13, wherein said plural ultraviolet bulbs form an arrangementselected from the group consisting of a random arrangement, aside-by-side arrangement, a sequential arrangement, an array arrangementand a cluster arrangement.
 16. An ultraviolet light source according toclaim 1, wherein the optically transparent waveguide has a cylindricalor rectangular form.
 17. An ultraviolet light source according to claim1, wherein the microwave energy source comprises a magnetron.
 18. Anultraviolet light source according to claim 1, additionally comprising asystem for cleaning the enclosure.
 19. An ultraviolet light sourceaccording to claim 1, additionally comprising a pathguide to guide themicrowave energy from the microwave energy source to the ultravioletbulb.
 20. An ultraviolet light source according to claim 19, wherein thepathguide defines an essentially linear path.
 21. An ultraviolet lightsource according to claim 19, wherein the pathguide defines a non-linearpath.
 22. An ultraviolet light source according to claim 19, wherein thepathguide comprises a coaxial cable.
 23. An ultraviolet light sourceaccording to claim 1, additionally comprising a housing for saidwaveguide.
 24. An ultraviolet light source according to claim 23,wherein the housing has an inlet and an outlet and the housing is shapedto guide fluid flow from the inlet, past the waveguide to the outlet.25. An ultraviolet light source according to claim 24, wherein saidfluid comprises water or air.
 26. An ultraviolet light source accordingto claim 24, additionally comprising a pump for pumping fluid from theinlet, past the enclosure to the outlet.
 27. A lamp comprising anultraviolet bulb, said bulb being excitable by microwave energy; and anoptically transparent waveguide for guiding microwave energy originatingfrom a microwave energy source to the ultraviolet bulb, wherein saidwaveguide wholly surrounds the ultraviolet bulb, and wherein thedominant wavelength of the lamp is either (a) from 140 to 240 nm and thelamp is suitable for use in promoting molecular dissociation reactions;or (b) from 300 to 400 nm and the lamp is suitable for use in promotingphotochemical reactions.
 28. A lamp according to claim 27, wherein thedominant wavelength of the lamp is from 160 to 200 nm.
 29. A lampaccording to claim 28, wherein the dominant wavelength of the lamp isfrom 330 to 370 nm.
 30. A lamp according to claim 27, wherein theultraviolet bulb has no electrode.
 31. A method of promoting thedissociation of a molecular entity comprising applying microwave energyto an ultraviolet lamp to produce ultraviolet radiation of dominantwavelength of from 140 to 240 nm; and exposing the molecular entity tosaid ultraviolet radiation, wherein an optically transparent waveguideguides said microwave energy to said ultraviolet lamp and said waveguidewholly surrounds the ultraviolet lamp.
 32. A method according to claim31, wherein the molecular entity is borne in a fluid such as air or aliquid and the substance-bearing fluid flows past the enclosure.
 33. Amethod according to claim 31, wherein the molecular entity is an organicmaterial.
 34. A method according to claim 33, wherein the organicmaterial is oxidisable.
 35. A method according to claim 34, for thedissociation of Total Oxidisable Carbon (TOC) in water.
 36. A methodaccording to claim 31, wherein the molecular entity is borne on asurface and the ultraviolet radiation is applied to said surface.
 37. Amethod according to claim 36, wherein the molecular entity is acontaminant on the surface.
 38. A method according to claim 36, whereinthe surface is of a product selected from the group consisting of foodproducts, packaging products and the surfaces of any equipment employedin the manufacture thereof.
 39. A method of promoting a photochemicalreaction in a substance comprising applying microwave energy to anultraviolet lamp to produce ultraviolet radiation having a dominantwavelength of from 300 to 400 nm; and exposing an entity to saidultraviolet radiation, wherein an optically transparent waveguide guidessaid microwave energy to said ultraviolet lamp and said waveguide whollysurrounds the lamp.
 40. A method according to claim 39, wherein thesubstance is borne in a fluid such as air or a liquid and thesubstance-bearing fluid flows past the enclosure.
 41. A method accordingto claim 39, wherein the substance is borne on a surface and theultraviolet radiation is applied to the surface.
 42. An ultravioletlight source comprising a plurality of ultraviolet bulbs; a microwaveenergy source for exciting said plurality of ultraviolet bulbs; and anoptically transparent waveguide for guiding microwave energy originatingfrom said microwave energy source to the plurality of ultraviolet bulbs,wherein said waveguide wholly surrounds the plurality of ultravioletbulbs.
 43. A lamp comprising a plurality of ultraviolet bulbs, saidplurality of bulbs being excitable by microwave energy; and an opticallytransparent waveguide for guiding microwave energy originating from amicrowave energy source to the plurality of ultraviolet bulbs, whereinsaid waveguide wholly surrounds the plurality of ultraviolet bulbs.